The present invention relates in general to analog arrays and, more particularly, to leakage current compensation in the analog array.
Analog circuits are used in a variety of applications for providing functions such as filters, gains stages, analog-digital converters, etc. In the past, analog circuits have been generally designed for custom applications with a fixed amplifier stage and dedicated passive and/or active elements in the feed-forward and feed-back paths to perform the desired function. Each new circuit application typically requires a new design phase and layout phase which is a time consuming and expensive undertaking.
To bring products to market more efficiently, field programmable analog arrays have been developed to allow flexible implementations of analog functions. A typical field programmable analog array includes a fixed amplifier with programmable switched capacitor banks on its input terminals and feedback paths. The user need only program the switches to set the impedance values as needed to perform the analog function.
A common problem associated with switched impedance type field programmable arrays is the large number of switches needed to perform a useful function and the associated leakage current into the input terminals of the amplifier due to the large number of switches. The leakage current originates from the diffusion area of the switch contacts. Any leakage current introduced into the input terminals of the amplifier causes a voltage drift at the output of the amplifier. The diffusion current varies with process and increases with temperature thereby adding to the problem.
Hence, a need exists to minimize leakage current into the input terminals of the amplifier or any charge storage node associated with the field programmable analog array.